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CHROME-TUNGSTEN STEELS                        !93

after fusion with sodium peroxide, the method employed being that given
on p. 184 for the determination of chromium in presence of molybdenum
^   5. Determination of the Nickel.—The method used in the case of
nickel steels is employed.

* *

Molybdenum steels contain on the average 0-5-5% of molybdenum (rarely
10-12%), with which chromium, nickel, etc., are often associated and they con
tain the proportions of carbon, silicon, phosphorus, etc., normally present in
ordinary steels.

Molybdenum steels with 3-4% Mo and i-t-5% C serve also for making
permanent magnets.


Silicon steels have a very high elastic limit and great resistance to shock
and are therefore used for making springs.

Their analysis includes essentiaUy determinations of the silicon and
carbon and of the other elements usually present in steels (Mn, P, S, etc.).

Each of these determinations may be carried out just as with wrought-
iron, steel and cast-iron (see Iron).

* *

The two commonest types of silicon steel contain respectively : (i) 0-45-
0-5% C and 1-5-1-2% Si and (2) 0-65-0-7% C and 0-9-0-8% Si. Silicon steels
with 2-3% Si and free from graphitic carbon, are used for dynamo sheet, rails,


Chrome-nickel steels exhibit the hardness of chrome steels and the
strength of nickel steels. They are used, therefore, for making machine
parts exposed to great stress, armour-plating, projectiles, etc.

1.  Determination of the Chromium and Nickel.—These are esti-
mated on two separate portions of the sample by the methods given for
chrome steel and nickel steel.

2.  Determination of the Carbon, Silicon, Manganese, Phosphorus
and Sulphur.—As with chrome steels and nickel steels.

* *

Chrome-nickel steels for machine parts have the following mean composition :
0-2-0-5% Cr, 2-5-2-8% Ni, 0-35% C; those for armour-plating : 0-2-0-9% Cr,
1-7-2-8% Ni, 0-2-0-4% C; an<3- those 'for projectiles, 0-65-2% Cr, 2-2-6% Ni
and 0-6-0-8% C.


These have the property of retaining their temper even at high tem-
peratures and are, therefore, used especially for making tools for metal

1. Determination of the Chromium and Tungsten.—2-3 grams
of the sample are treated with nitric acid, evaporated and calcined, the
oxides obtained being fused with sodium peroxide as for chrome steels.

A.C.                                                                                                       13ation of the trioxide) the weighed oxides are dissolved